Known in the art are electrical boxes intended to enclose wiring and connectors, those boxes also optionally including mountings for securing a lighting fixture. Certain of those boxes are suitable for mounting overhead just above a ceiling, attaching to a truss, joist or other structural support member. In a typical new installation metal or, more frequently, plastic light-duty boxes are installed, those being the most inexpensive type suitable for carrying a light-weight lighting fixture, for example a fixture housing a single medium-base bulb. It is often the case that a homeowner will wish to later install a heavier fixture, such as a ceiling fan or chandalier, to the originally installed electrical box. Many homeowners are not aware of the unsuitability of these light-weight boxes for those applications, and many install these heavier fixtures improperly and dangerously without upgrading the support structure.
A ceiling fan, through normal operation, may create oscillatory stresses on the electrical box it is attached to. If attached to a light-duty box, these forces may carry through the fan support to the electrical box, which may cause the box to twist slightly on each oscillation. Over time this motion may cause the nails, or other fasteners, used to secure the electrical box to move and/or loosen, which may lead to failure of the electrical box supporting structure. Additionally, if the box structure is not sufficiently rigid, forces may be transferred to the drywall, or other material, of the ceiling. Now drywall, plaster, paneling and most other ceiling materials are not designed to carry loads. These materials may carry a load briefly, but over time cracks may develop leading to an unpredictable failure of the material. If both the electrical box supporting structure and the ceiling material fail, the result is a fixture falling at an unpredictable time, which can lead to property damage, personal injury and litigation against the makers of the ceiling fan, lighting fixture, electrical box manufacturer as well as other involved parties.
In many areas earthquakes are a concern. A non-moving ceiling fixture mounted to a light-weight box may carry a load sufficiently well under static conditions for many years. Earthquakes are unpredictable events that may occur at any time, and in some locations with such severity as to cause large thrust and oscillatory motions on the lighting fixture and electrical box. A homeowner may be completely unaware of a dangerously supported fixture until a tremor causes it to fall. The dangers of inadequately supported lighting fixtures therefore encompasses more fixtures than ceiling fans.
Now there are several electrical box types which will support a relatively heavy load, of which several are represented in U.S. patents. A usual type, represented by U.S. Pat. No. 6,242,696 utilizes wings attached to the side of the electrical box to attach to a structural member. This type requires installation prior to the installation of a finished ceiling to avoid damage thereto. Another type, represented by U.S. Pat. Nos. RE 38,120, 6,107,568, 6,191,362, 6,207,897 and 6,355,883 envisions a ceiling electrical box that attaches to an overhead structural support member from underneath through the use of screws or other fasteners generally driven upward through the top of the box and into the structural member. Those boxes either include a slot fitting the support member, or are designed to fit in a space between the support member and the surface of the finished ceiling. All of those designs have the disadvantage of reduced internal box volume, by which the number of electrical connections and wires is restricted over a common side-mounted nailed electrical box. Another type, represented by U.S. Pat. Nos. RE 33,147, 6,098,945, 6,465,736, and 6,595,479 utilizes an extendable rod or other structure fittable between the space between two joists or structural members. This type of electrical box, although avoiding impacts into the volume of the electrical box, carries a number of disadvantages. First, the use of the rod introduces a substantial lever arm; the rod must therefore be fairly heavy to avoid bowing under the fixture load. This type of box is typically constructed of steel or other metal, as the needed plastic supports would be very thick in comparison. These boxes tend are more complex and require more materials and building steps to fabricate. The cost of this type of box tends to be much higher to the end user. A final type, represented in U.S. Pat. Nos. RE 34,603 and 6,100,469, utilizes fasteners through a metal electrical box sidewall into the adjacent structural member. This type relies on the strength of the sidewall to avoid the fastener head pulling through the sidewall material under load, and is therefore unsuitable for plastic materials. Furthermore, this type relies on the box structure to resist a downward force, which may place strain on welds and joints. Additonally, fasteners driven in a substantially horizontal direction limit the amount of driving force that can be applied to the fastener and may make installation difficult without specialized tools. And none of these box types provide a method of upgrading a ceiling electrical box to carry additional load.
Thus, some of these boxes are relatively expensive to produce and install, while others may be installed only by creating new holes in a ceiling or otherwise causing new damage that must be repaired. In the market there is a general lack of products and methods that provide for upgrading of ceiling electrical boxes to support heavier loads. There is therefore a need for products which can create a box structure capable of supporting more than a light load which can be installed without causing damage to an existing ceiling.